(+ left (* count (/ (- left right) count)))

Average Error: 15.2 → 0

Time: 806.0ms

Precision: binary64

• could not determine a ground truth for program body

  1. left = -9.670211746472374e+192
  2. count = 1.0741547877035668e-05
  3. right = -1.3981953459461208e+194

Math

\[left + count \cdot \frac{left - right}{count}\]

↓

\[\left(left + left\right) - right\]

C

double code(double left, double count, double right) {
	return ((double) (left + ((double) (count * ((double) (((double) (left - right)) / count))))));
}

↓

double code(double left, double count, double right) {
	return ((double) (((double) (left + left)) - right));
}

Error

Bits error versus left

Bits error versus count

Bits error versus right

Derivation

1. Initial program 15.2

   \[left + count \cdot \frac{left - right}{count}\]

2. Simplified 0

   \[\leadsto \color{blue}{\left(left + left\right) - right}\]

3. Final simplification 0

   \[\leadsto \left(left + left\right) - right\]

Reproduce

herbie shell --seed 2020153 
(FPCore (left count right)
  :name "(+ left (* count (/ (- left right) count)))"
  :precision binary64
  (+ left (* count (/ (- left right) count))))